Get current item value from a dropdown menu?
The solution was to add a update to the prop. Then i can retreive changes from the dropdown box.

def myindex(self, context):
    print('changed to,', context.scene.MyEnum)
...

bpy.types.Scene.MyEnum = bpy.props.EnumProperty(items = item_cb, update = myindex)  


Another way goes directly across int(context.scene.MyEnum). Then i don't need the update.